Measurement of Deformation and Strain in First Level C4 Interconnect and Stacked Die using Optical Digital Image Correlation

Abstract

In this paper, we demonstrate the application of digital image correlation (DIC) to the measurement of nanometer scale deformation in advanced packaging including flip chip and stacked integrated circuit dies. The application of DIC is shown to provide critical strain data which is useful for lifetime prediction of advanced packaging solutions. We show U and V deformation field contour (fringe) maps, analogous to Moire interferometry results, measured by digital image correlation technology, without the need for applied phase gratings. Shear and normal strain contour maps are also shown superimposed transparently on micrograph images. Novel enhancements of the digital image correlation technique are described with particular emphasis on the refinement of the technique for application to electronics package measurement, and on software development. The application of levels of intelligent, goodness-of-data based corrections, for the measurement of nanometre scale deformation, and rigid body motion corrections are discussed. The technique has been further refined to obtain measurements from entire IC package structures which include such thermally and optically distinct materials as underfill and copper layers. Finally, failure analysis and modeling, such as Norris-Landzberg or Coffin-Manson models, is discussed in relation to the results exposed in this paper.